Why can't I access wifi on my pre owned Galaxy S6 unlocked Vodafone

I've recently obtained a pre owned Galaxy S6 off ebay. The phone is unlocked but with a text message from Vodafone message - You've swapped your SIM To keep using data and picture messaging you may need to update your settings. we'll send you these shortly. It was sent from UK to me in Spain. The internet message is - err. internet disabled. I am unable to connect to home WiFi. Will obtaining a new SIM package in Spain rectify the problem? Or am I doooomed!!
Look forward to your help. Android phone illiterate OAP

The SIM has nothing to do with Wifi. Neither should the settings they're sending you - which should be the APN settings.

Try Forgetting the wifi connection, then setting it up again. Unless there's a hardware problem, you should be able to connect to any public wifi (you might need to open a browser to get an internet connection on some) or any home wifi you have the password to.

I'm not able to access the internet in any way. There is a your device is offline - err. internet disconnected message when I try to turn it on The on/off internet button stays grey colour. How can I activate this button?
Thanks, Android illiterate, OAP

Are you trying to turn Wifi or Mobile data on? They're in 2 different places in Settings. (Wifi is the same all over, mobile data may not be. The phone may not be usable in Spain for mobile data, oe ir may just not be usable on your carrier for mobile data.)